General Claiming your losses

It has been said that you are required to report all the money you win as taxable income. What of the gambling losses? I have always known that these are tax deductible but then I believe there is a minimum threshold after which you are required to report your winnings. How then can you claim your losses?

I'd never thought about that! Is it possible to claim gambling losses as a tax expense if I gambled on vacation? Would I have to be a pro to do it?